The field site for this TMRC will be INSALPA, the Health Institute of the Pacific (Instituto de Salud del Pacifico. INSALPA was organized in 1987 is a center for malaria field studies. It is located in Buenaventura the main port on the Pacific coast (250,000 inhabitants), the most severe malaria endemic region of Colombia. INSALPA has laboratories for malaria diagnosis, an insectary with an A. albimanus colony and a unit for Epidemiology. Through an agreement between INSALPA and the District Hospital in Buenaventura, a Clinical Unit for tropical diseases was jointly created in the Hospital. The Institute has in addition, lecture rooms and teaching facilities that are used for continuous medical education. Due to the central location of Buenaventura on the Pacific coast, most people from peripheral areas requiring medical attention go to the District Hospital contiguous to the INSALPA building. In addition, multiple villages around Buenaventura, distant from 10 50 Km have malaria transmission. The malaria diagnosis laboratory together with the insectary, provide readily available resources for this project. During the last years this facility has been the field station used by the Immunology Institute as a base for its immuno-epidemiology studies. From this location many malaria endemic villages are accessible making possible to obtain human blood specimens for cellular immunity studies. In addition, the daily availability to malaria-infected patients at the diagnostic unit has contributed to the studies requiring wild parasite isolates for gene polymorphism and drug resistance. The possibility of obtaining blood samples carrying Plasmodium gametocytes and the availability of mosquitoes, have made feasible the regular production of sporozoites during the last two years. This in vitro system will be of great usefulness for the proposed studies on Transmission Blocking immunity. This Core facility will also be essential for the analyses of the natural immune response of humans to P. vivax antigens and for the evaluation of natural gene polymorphism of the antigens under study.